Add shape cuts pocket/profile/contour

[tirithen]

As work with the clipper2 is now complete enough, that unlocks possibilities for pocket/profile/contour cuts from 2d shapes.

• Create a shape struct that represents a set of paths
• Add shape helpers for basic shapes such as rectangles and segmented circles
• Parse paths from SVG files into a shape
• Allow boolean operations between shapes with the help of the clipper2 crate
• Add pocket cut
• Add profile cut (with "border" thickness selection)
• Add contour cut (with inner/outer tool compensation)